This relates generally to imaging devices, and more particularly, to imaging devices having pixel arrays with per-pixel gain adjustment capabilities.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. In a typical arrangement, an electronic device is provided with an array of image pixels arranged in pixel rows and pixel columns. Row control circuitry is coupled to each pixel row over row control lines for providing pixel control signals to each image pixel in the pixel row. Image pixels are often operated in a low gain mode for capturing images of brighter scenery and in a high gain mode for capturing images of darker scenery.
In conventional imaging systems, row control circuitry provides control signals to each pixel in a selected pixel row that instruct every pixel in that row to operate in either the high gain mode or the low gain mode. However, scenes to be imaged often include both brighter and darker portions across any given row of image pixels. Performing image capture operations using conventional image sensors that control image pixels in an entire pixel row to operate in the high gain or low gain mode may thereby cause some image pixels in a given pixel row to generate excessively noisy or over-saturated image signals, which can generate unsightly image artifacts in the final captured image. During conventional image sensor operation, gain adjustment control signals provided to a row of pixels to place the row into high or low gain modes are typically boosted to voltage levels that are greater than a supply voltage level provided to the row of pixels. However, providing boosted gain adjustment control signals can induce voltage stress on the image sensor and can undesirably limit the lifetime of the image sensor.
It would therefore be desirable to be able to provide imaging devices with improved means of capturing and processing image signals.